Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming, and ultimately very expensive endeavors. As a result, over the years, a significant amount of added emphasis has been placed on well monitoring and maintenance. Once more, perhaps even more emphasis has been directed at initial well design and construction. All in all, careful attention to design and construction efficiencies may help maximize return on the substantial investment dedicated to oilfield operations.
In the case of well construction, careful attention and planning may be devoted to the specific architecture, drilling, casing and other hardware installations involved in what is generally referred to as ‘completions’ operations. Completions operations generally involve the positioning of large scale surface equipment at the oilfield. For example, a rig is located over a well head to serve as a platform for equipment access in drilling the well, installing various hardware or downhole devices, or to provide access for later well interventions.
In the case of initial installations, a variety of tubulars are often provided downhole from the rig floor. For example, casing segments to help support and define the well may be transported one by one into the well from the rig floor. This is no small feat given that each 20-40 foot casing segment is generally several thousand pounds of stainless steel tubing, up to a few feet in diameter. Thus, even getting the segments safely and efficiently to the rig floor for subsequent well installation is no small feat.
The noted heavy casing is generally pulled to the area of the rig floor by way of a rig elevator which may consist of a strap or cable at the end of a crane. That is, an operator at the rig floor may secure the strap about a collar of the casing segment thereby allowing the segment to be pulled upward to a vertical position for subsequent delivery into the well. Due to the massive size of the casing, a positioning system, generally referred to as a ‘Laydown’ or ‘Pickup’ Machine, is often used to convey each tubing segment to the vicinity of the rig floor where the noted strap may then be employed to pull the segment up vertically above the floor.
Unfortunately, a pickup machine is a large footspace eating piece of heavy immobile equipment, generally disposed at the oilfield surface on a skid. It may take several operators and multiple 18 wheelers to deliver, position and operate this equipment along with managing a supply of casing tubulars from an associated pipe rack. Once more, in spite of robust construction, the pickup machine is particularly prone to wear and failure. Specifically, a considerable amount of time and effort is dedicated to ensuring that a gantry system of rollers remains operable. This roller system is utilized to extend a trough accommodating each casing segment, one by one, toward the rig floor. Due to the amount of weight accommodated and the moving parts involved, such a system is prone to rapid wearing.
In addition to the massive size and failure modes of a pickup machine, it is also a very expensive piece of equipment, perhaps upwards of $250,000 in today's numbers. Once more, such drawbacks are particularly noteworthy where smaller, lighter weight specialty tubulars are involved. For example, even where lighter weight, say 500-600 lb. production tubing, is to be installed, the same type of large-scale pickup machine is generally employed. This is because, in spite of the lighter weight, such specialty tubing segments are generally of similar lengths, thus benefitting from the trough type of loading and extension delivery to the area of the rig floor.
Trough loading and extension also provide vastly improved safety as compared to say strap pickup from the oilfield surface. For example, a broken strap with the tubular resting at least partly more stably in a trough is much less likely to result in operator injury than a broken strap with the tubular fully suspended in mid air, perhaps 10 feet or more off the ground. As a result, even though the pickup machine is particularly prone to wear of its gantry system and may constitute overkill in terms of delivery capacity when utilized for lighter specialty tubulars, it nevertheless remains the preferred mode of tubular delivery to the rig floor.